Capsule for food or beverage preparation comprising an oversized membrane

ABSTRACT

The invention relates to a capsule (1) for food or beverage preparation, the capsule (1) comprising a hollow body (2) adapted to be punctured for fluid injection inside the capsule (1), a chamber (10) formed inside the body (2) and containing an ingredient, a membrane (9) covering an opening formed in a bottom end of the chamber (10), an edge of the membrane being fastened to a rim (12) surrounding the opening by fastening means which forms a seal between the body (2) and the membrane (9), and opening means disposed outside the chamber (10) in the vicinity of the membrane (9) configured to open the membrane when it is pressed against said opening means under an opening pressure. The part of the membrane (9) which is surrounded by the seal has a developed surface area comprised between 110% and 140% of the area of a flat surface surrounded by said seal.

FIELD OF THE INVENTION

The present invention concerns the field of food or beverage capsules comprising a hollow body which contains an ingredient for food or beverage preparation. In the field of food or beverage preparation, it is known to use single-serve capsules for mixing an ingredient contained in said capsule, with a fluid fed from a pressurized source contained in a food or beverage preparation machine. More particularly, such capsules are adapted for preparation of a food or beverage preparation by dissolution into the fluid or extraction by the fluid under a preparation pressure. This includes preparation of coffee (in such case, the ingredient is ground roasted coffee to be extracted into water vapour and/or hot liquid water), and soluble ingredients or a mix of soluble ingredients for preparation of a beverage such as instant coffee, hot chocolate, or a soup or other dehydrated edible product to be dissolved into hot or cold water or milk.

BACKGROUND OF THE INVENTION

The principle of extracting and/or dissolving the contents (i.e. ingredients) of a closed capsule under pressure is known, and consists typically of inserting the capsule into a receptacle or cavity of a machine, injecting a quantity of pressurized water or other adapted fluid into the capsule, generally after piercing a face of the capsule with a piercing injection element such as a fluid injection needle mounted on the machine, so as to create a pressurized environment inside the capsule either to extract the substance or dissolve it, and then release the extracted substance or the dissolved substance through the capsule.

Capsules have been developed for such an application of food preparation, and in particular for beverage preparation, which are described and claimed in applicant's European patent EP 1784344 B1, or in European patent application EP 2062831.

In short, such capsules comprise typically:

-   -   a hollow body comprising an injection wall which is impermeable         to liquids and to air and which is attached to the rest of the         body (or made integral with the body) and adapted to be         punctured by e.g. an injection needle of the machine,     -   a chamber containing a bed of ground roasted coffee to be         extracted, or a soluble ingredient or mix of soluble         ingredients,     -   a membrane, usually made of aluminium, disposed at the bottom         end of the capsule and fastened to the body.

The membrane closes the chamber, for retaining the internal pressure in the chamber when pressurised fluid is introduced into the capsule.

The opening of the chamber for beverage delivery is achieved by increasing the pressure within the chamber. This pressure is increased by introducing a quantity of pressurized fluid such as water into the chamber. When the internal pressure is sufficient, the membrane is opened upon contact with opening means. The present invention relates to a capsule having the opening means within the capsule, or in other words a capsule which comprises its own opening means activated by the rise of pressure of the fluid introduced into the capsule at the time of beverage extraction. This type of capsule is disclosed for example in European patent application EP 1472156. Opening means are disposed within the capsule, outside the chamber, in the vicinity of the membrane. When a sufficient pressure is established inside the chamber, the membrane tends to be pressed against said opening means, and is ruptured, and thus opened. The beverage flows through the openings thus produced.

The opening means are for example formed by a so-called “pyramid plate” comprising raised and recessed elements. The membrane engages the raised and recessed elements of the pyramid plate under the effect of the rise of pressure in the chamber of the capsule until it the membrane ruptures and opens.

Correct engagement of the membrane with the opening means has to be obtained to provide a safely reproducible pressure inside the capsule when a food or beverage product is prepared, and also to provide an efficient filter function to the membrane in cooperation with the opening means.

Indeed, the membrane has to take the shape of the opening means as much as possible before it opens. Correct engagement corresponds to a state in which the membrane is deformed so as to cover a given percentage, e.g. at least 60%, of the overall developed surface area of the opening means (i.e. of the surface of the opening means in the vicinity of the membrane before a rise of the pressure inside the capsule).

However, the membrane has to be made of a material that is stiff enough to allow the pressure to rise inside the chamber up to the desired level. The membrane is generally made of aluminium. This material is convenient to form the membrane, and its implementation in a food or beverage capsule is well known. However, the mechanical properties of the material does not allow the membrane to be stretched to a great extent before it ruptures.

The present invention thus relates to a capsule for food or beverage preparation configured to address the above-mentioned problem.

SUMMARY OF THE INVENTION

According to the invention, there is provided a capsule for food or beverage preparation, the capsule comprising:

-   -   a hollow body which is impermeable to liquids and to air and         which is adapted to be punctured for fluid injection inside the         capsule,     -   a chamber formed inside the body and containing an ingredient         for preparing food or beverage by dissolution into the fluid         under pressure or extraction by the fluid under pressure,     -   a membrane fastened to the body to retain pressure in the         chamber, at least part of said membrane covering an opening         formed in the bottom end of the chamber, the opening being         surrounded by a rim to which an edge of the membrane is fastened         by fastening means which forms a seal between the body and the         membrane, and     -   opening means disposed outside the chamber in the vicinity of         the membrane, the opening means being configured to open the         membrane when said membrane is pressed against said opening         means under an opening pressure.

The part of the membrane which is surrounded by the seal has a developed surface area comprised between 110% and 140% of the surface area of a flat surface surrounded by said seal.

The capsule according to the invention thus provides extra-surface area (compared to the prior art) for the membrane to engage the opening means without being stretched, or at least without being much stretched. The membrane is pushed in a direction outwardly of the chamber when a pressure, more than the atmospheric pressure, is established inside the chamber by introduction under pressure of a fluid for food or beverage preparation. The membrane thus protrudes from the chamber, before being elastically or plastically deformed, to engage the opening means.

The opening formed in a bottom end of the chamber can have an area of about 600 mm² while the part of the membrane which covers this opening has a developed surface area of more than 750 mm².

The fastening means can comprise an adhesive seal band.

The membrane can be formed from a flat sheet having a periphery of greater length than a periphery of the rim which surrounds the opening, the length of the periphery of the membrane in excess compared to the length of the periphery of the opening rim being evenly distributed along said periphery of the opening rim.

The opening formed in the bottom end of the chamber can be substantially circular, and the membrane can form a dome over the opening formed in the bottom end of the chamber when a pressure is established in the chamber (10) greater than the pressure outside the chamber.

The part of the membrane which covers the opening formed in the bottom end of the chamber can comprise folds so as to be substantially flat when the pressures on each side of the membrane are balanced. The membrane can be at least in part unfolded under the effect of a pressure established in the chamber.

One of the difficulties in implementing the invention is the way to arrange the membrane on an opening of smaller dimensions, and to fasten the membrane periphery to a fastening area of smaller dimensions such as a rim surrounding the opening. Use of an adhesive seal band such as a heat seal lacquer makes it possible to fasten an edge of the membrane to such rim even if the periphery of the membrane is of greater length than a periphery of the rim which surrounds the opening. The adhesive seal band material can be chosen from known materials used in the food industry.

For example, small folds are created at the periphery of the membrane to reduce its apparent length. The heat seal lacquer band conforms to the small irregularities formed by the folds at the periphery of the membrane to provide fluid-tight sealing between the membrane and the body of the capsule.

If the membrane is fastened to the body by a circular adhesive seal band it will tend to adopt a dome shape inside the chamber of the capsule. To maximise the volume of the chamber the so-configured membrane can be flattened by creating folds which are unfolded when a high pressure is established inside the chamber.

The opening means can comprise (or be constituted by) a plate having an upper surface facing the membrane, and the upper surface forms or carries sharp elements. The sharp elements can be pyramids or truncated pyramids.

A plate having an upper surface carrying truncated pyramids or other sharp puncturing elements provides an advantageous configuration because such a surface acts as a pressure-spreading means and has the effect of allowing the pressure of the fluid to rise sufficiently inside the capsule before puncturing (and opening) of the membrane occurs. In cooperation with the membrane, it provides a filter function to avoid ingredient such as ground roasted coffee being delivered with the prepared beverage.

The part of the membrane which covers the opening formed in the bottom end of the chamber can have a surface area of more than 60% of the developed surface area of the plate.

Such configuration allows the membrane to correctly engage the opening means, it allows the membrane to correctly conform to the shape of said opening means and it provides an efficient cooperation between the membrane and the opening means to provide a filter function.

The membrane is for example made of aluminium, or of a laminate structure comprising an aluminium foil and a polymer layer. Alternatively, the membrane is for example made of plastics with a metallic covering. The membrane can comprise pre-weakened spots.

The invention makes it possible to use very stiff (with low or no elasticity) membranes while a correct engagement of the membrane with the opening means can be reliably obtained.

The material of which the chamber is formed can be at least one of aluminium, aluminium/plastics composite, aluminium/plastics/paper composite, and plastics in a single layer or in a multilayer form.

The ingredient contained in the chamber can comprise ground roasted coffee to be extracted into water vapour and/or hot liquid water or comprises a soluble ingredient or mix of soluble ingredients for preparation of a beverage such as instant coffee, hot chocolate, or a soup or other dehydrated edible product to be dissolved into hot or cold water or milk.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional features and advantages of the present invention are described in, and will be apparent from the description of the presently preferred embodiments which are set out below with reference to the drawings in which:

FIG. 1 is a schematic perspective view in cross-section of a capsule for food or beverage preparation according to the prior art;

FIG. 2 is a schematic perspective view in cross-section of a capsule for food or beverage preparation according to an example embodiment of the invention;

FIG. 3 is a schematic perspective view of a pyramid plate which constitutes opening means that can be used in a capsule according to the invention;

FIGS. 4a to 4c are schematic partial cross-section views of a capsule which illustrate the behaviour of a membrane of a capsule according to the prior art;

FIGS. 5a and 5b illustrate on similar views as FIG. 4a two alternative embodiments of a capsule according to the invention;

FIGS. 5c and 5d illustrate on a similar view to those of FIGS. 4b and 4c the behaviour of a membrane of a capsule according to the invention when a high pressure is established inside the capsule chamber.

DETAILED DESCRIPTION OF THE INVENTION

The capsule 1. of FIG. 1. comprises a capsule body 2 made of capsule walls 3. In the represented embodiment, the capsule body walls 3 have a substantially frusto-conical shape

The capsule walls 3 can be made of different materials. They can be made of aluminium, aluminium/plastics composite, or aluminium/plastics/paper composite. They can be made of a rigid or semi-rigid thermoplastics such as a polypropylene or polyethylene. Plastics can be in a single layer or in a multilayer form. The capsule body can for example also be made of any suitable type of impermeable material such as coated paper, coated cardboard, other materials containing cellulosic fibres, or starch for instance, metal or alloy, glass, synthetic or natural rubber or elastomer, or a combination thereof. Preferably, materials will be chosen from cost-effective and ecologic material, e.g. biodegradable material, having barrier properties, preferably at least against moisture and oxygen.

Depending on the material used, the manufacturing process can be thermoforming or injection. It can also involve in-mould labelling, for instance in order to provide the capsule with specific barrier properties by using a film label with moisture and oxygen barrier properties. Such an in-mould labelling process for making a capsule is generally described in the applicant's European patent publication EP 2559636 A1. The moisture and oxygen barrier properties of the container walls can be achieved with any kind of suitable material such as barrier thermoplastics films having single or multiple layers, or aluminium, or paper, or a combination thereof. The capsule body walls 3 comprise upper and lower openings.

The upper opening of the capsule body is closed by an upper injection wall 4 forming the top face 5. The upper injection wall 4 can be welded on upper peripheral edges 6 of the capsule body walls 3.

The capsule 1 further comprises a bottom wall 7 having a dispensing opening 8. It further comprises a pierceable membrane 9, for example made of aluminium. The membrane 9 is preferably made of a laminate structure comprising an aluminium foil and at least a polymer layer. More particularly, the membrane 9 can comprise a sealing layer that makes it possible to fasten the aluminium foil to the body of the capsule (for example made of plastics). Optionally, a top layer of protective lacquer can be provided to prevent the aluminium foil from damages caused by the aggressive powder particles of ingredient contained inside the capsule. The membrane 9 is fastened to the capsule body 2. A chamber 10 is thus formed within the body 2, delimited by the body walls 3, the injection wall 4, and the membrane 9.

The membrane 9 is fastened to the body 2 by an adhesive seal band 11. The adhesive seal band 11 provides sealing between the body 2 and the membrane 9.

More particularly, the chamber 10 is closed at its bottom end by the membrane 9, the bottom end of the chamber 10 comprising an opening closed by said membrane 9. The opening at the bottom end of the chamber 10 is surrounded by a rim 12. The rim 12 extends in a plane parallel to the top face 5 of the capsule, and provides a flat surface for fastening the membrane 9. The adhesive seal band 11 is interposed between said rim 12 and a periphery of the membrane 9.

The capsule 1 of the represented example embodiment further comprises a rigid distributor wall 13 that is located between said injection wall 4 and a capsule lower compartment 14.

Preferably, the ingredient contained in the capsule is located in the interior compartment 14, i.e. in the portion of the capsule chamber 10 which is between the distributor wall 13 and the bottom membrane 9.

However, it is also possible to dispose the same ingredient throughout the whole volume of the chamber 10, or alternatively, two different ingredients can be separated from one another by the distributor wall 13.

The distributor wall 13 comprises through-holes. Their diameter is appropriately chosen depending on the type of ingredient contained in the capsule and on the corresponding type of product preparation. If the distributor wall comprises a single hole, the flow of fluid through said hole will create a single jet, with a powerful mixing effect. This configuration is preferably chosen in case the ingredient contained in the capsule is a soluble powder, which requires a powerful swirling movement of the water injected therein, so as to improve the dissolution of the powder with the water. Alternatively, for example if the ingredient contained in the capsule compartment is ground roasted coffee, the distributor wall 13 comprises a plurality of holes, distributed evenly across its surface to ensure proper wetting of the coffee bed contained between the distributor wall 29 and the bottom wall 32 of the capsule.

The diameter of the holes is preferably less than the smallest particles of the ingredient, but it is sufficient to ensure a proper flow of water through the rigid distributor wall 13. The diameter can for example be comprised typically between 10 microns and 3 mm, preferably between 100 microns and 1 mm.

Between the membrane 9 and the bottom wall 7, opening means 15 are provided. The opening means 15 has the general shape of a plate, the upper face of said plate facing the membrane 9 and being disposed inside the capsule body 2 in the vicinity of the membrane 9. The upper face of the plate of the opening means forms sharp elements adapted to pierce or tear the membrane 9 when fluid pressure inside the capsule compartment increases thus engaging the membrane with the opening means 15 and pressing said membrane against said opening means.

FIG. 2 represents an example embodiment of a capsule according to the invention, shown on a similar view to FIG. 1.

The general configuration of the capsule of FIG. 2 is identical to the general configuration of the capsule of FIG. 1, except for the membrane 9. The above detailed description of the capsule of FIG. 1 is thus applicable to the capsule of FIG. 2, with the following differences.

The membrane 9 of the prior-art capsule of FIG. 1 is usually made of a flat aluminium foil (or a foil of an adapted material) cut to the right dimensions to cover the opening at the bottom end of the chamber 10 and to rest on the rim 12 to which it is fastened by fastening means such as an adhesive seal band (e.g. made of a heat seal lacquer) which forms a seal between the membrane 9 and the rim 12. When the membrane 9 is not subject to a pressure difference between the inside and the outside of the chamber, it is substantially flat.

According to the present invention and as shown in FIG. 2, the part of the membrane which is surrounded by the seal has a developed surface area comprised between 110% and 140% of the area of a flat surface surrounded by said seal. In other words, the part of the membrane surrounded by the fastening means has a surface area which is 10% to 40% greater that the corresponding surface area of the flat membrane according to the prior-art shown in FIG. 1. This implies that the part of the membrane 9 surrounded by the fastening means cannot be flat. If the seal formed by the adhesive seal band 11 is substantially circular, this part of the membrane 9 can have the shape of a dome.

As in the prior-art, the membrane 9 can be obtained in a flat aluminium (or other adapted material) foil. For example, if the rim 12 where the membrane is fastened is circular, a circular membrane 9 of greater diameter than the diameter of the rim 12 can be used. The periphery of the membrane 9 is thus of greater length than the periphery of the rim 12 which surrounds the opening. The excess length of the membrane periphery can be evenly distributed along the periphery of the rim 12. In particular, small folds can be made at the periphery of the membrane 9 to arrange the membrane 9 on the rim 12 having a smaller periphery.

Thanks to the use of an adhesive seal band such as a heat seal lacquer as fastening means, a fluid-tight seal can be provided despite the surface irregularities caused by the folds at the periphery of the membrane 9.

As hereafter described with reference to FIGS. 4a to 5d , the greater surface area of membrane compared to a capsule according to the prior art will help the membrane 9 to correctly engage the opening means 15 and to conform to the same when a pressure higher than atmospheric pressure is established in the chamber 10 when fluid for food or beverage preparation is injected into the chamber 10.

FIG. 3 is a detailed perspective view of an example embodiment of the opening means 15, corresponding to the opening means used in the capsule of FIG. 1. The upper face the opening means 15 is shown in FIG. 2. According to this embodiment the opening means 15 for opening the membrane 9 consist of a disc with recessed and raised elements 16. The recessed and raised elements 16 have a pyramid-shape (more precisely a slightly truncated pyramid shape). In other embodiment, the recessed and raised elements have any other geometry adapted to open the membrane, such as a cone shape. Smaller raised elements 17 are also arranged in spaces 18 between the pyramidal raised elements 16.

The plate comprises holes preferably formed in the spaces 18 between the pyramidal raised elements 16 (e.g. at the top of said smaller raised elements) so as to let the product formed by dissolution or extraction inside the compartment 14 out towards a consumer's cup when the membrane 9 is opened.

As the membrane engages and is pressed against the upper face of the opening means, the membrane has also a filter function for the prepared beverage.

The membrane has to correctly engage with the opening means, and in particular it has to be deformed and stretched to conform to the pyramid surfaces (or the surfaces of other opening elements) to provide, in a reproducible way, a regular opening such as holes or tears evenly distributed over the surface of the membrane, and also to provide a filter function to avoid particles of ingredient being delivered with the food or beverage product. To enhance reproducibility of the membrane opening, the membrane can comprise pre-weakened spots. The pre-weakened spots can advantageously be placed to match the raised elements of the opening means when the membrane engages said opening means.

FIGS. 4a, 4b and 4c illustrate the behaviour of a membrane of a capsule according to the prior art when a food or beverage product is produced.

FIG. 4a represents the bottom end portion of a capsule for food or beverage preparation, before injection of fluid inside the chamber 10. The membrane 9 is fastened to rim 12 formed by the walls 3 of the body 2 by the adhesive seal band 11. As the pressure is balanced between the interior of the capsule (chamber 10) and the exterior of the capsule, no force due to a pressure difference is applied to the membrane 9. In this state, the exterior surface of membrane 9 (face of the membrane outside the chamber 10) faces the opening means 15 in the vicinity of an upper face of said opening means 15.

In FIG. 4b , fluid, typically water and/or water vapour is introduced under pressure (i.e. above atmospheric pressure) into the chamber 10 formed within the capsule body 2. The pressure rises inside the chamber 10. The pressure is applied to the body walls 3 and to the membrane 10. More particularly, the pressure is applied to the part of the membrane 9 which closes the opening surrounded by the rim 12. The pressure difference between the interior of the capsule (chamber 10) and the exterior of the capsule, in particular under the membrane 9, generates a force distributed over the membrane surface area which closes the opening surrounded by the rim 12. This force pushes the membrane 9 in a direction from inside to outside the chamber 10. The membrane 9 engages the opening means 15. As shown in FIG. 3b , because the membrane is made of a stiff material such as aluminium, the deformation of the membrane 9 is limited. More particularly, the increase of the membrane surface area, i.e. the ability of the membrane to be elongated before it ruptures, is limited. The membrane thus conforms only to the top part of some of the raised elements of the opening means.

The pressure rises in the chamber 10 with introduction of fluid until it reaches a so-called opening pressure. With the pressure rise inside the chamber the membrane is pressed against the opening means by the force generated by the pressure difference between the pressure inside the chamber 10 and the atmospheric pressure outside said chamber 10. When the opening pressure is reached, the membrane opens (i.e. is pierced, cut, or torn) as shown in FIG. 3c thanks to the raised elements 16 of the opening means 15 that create a mechanical lever effect onto the membrane, hence a mechanical stress in the membrane material until the latter reaches its mechanical failure point and tears or more generally breaks. This breaking of the material does not necessarily need to be in a plane perpendicular to the general plane of the membrane, but can also be in any other direction, and not necessarily throughout the whole thickness of the material, as long as a passage is created between the inside of the capsule and the outside, so as to allow product to flow from inside the capsule towards the outside. The food or beverage product obtained flows through the membrane 9 and the opening means 15 to be delivered by the dispensing opening 8.

However, because the conformation of the membrane to the raised element is limited before it is opened, the membrane can have an irregular opening: the opening can be irregularly distributed on the membrane surface in contact with the opening means, the membrane can be ruptured before it conforms to the opening means (so that the pressure drops and the beverage flows through an opening of the membrane having an undesired shape). The opening of the membrane can also be different from one capsule to another. The filter function of the membrane 9 in cooperation with the opening means can change from one capsule to another. Particles of the ingredient contained in the compartment 14 (or generally speaking in the chamber 10) can pass through the membrane and opening means. For coffee preparation, this can lead to coffee having an unpleasant taste or texture.

The bad reproducibility of the opening of the membrane and its filter function from one capsule to another can change the quality or the taste of the prepared food product or beverage, because the pressure inside the chamber during the beverage preparation can change from one capsule to another, and because the filter function of the membrane and opening means can be modified.

By way of comparison, FIGS. 5a, 5b, 5c and 5d illustrate the behaviour of a membrane of a capsule according to the invention when a food or beverage product is produced.

More particularly, FIGS. 5a and 5b illustrate on similar views to FIG. 4a two alternative embodiments of a capsule according to the invention, and FIGS. 5c and 5d illustrate on a similar view to those of FIGS. 4b and 4c the behaviour of a membrane of a capsule according to the invention (e.g. according to the embodiments of FIGS. 5a and 5b ) when a high pressure is established inside the capsule chamber.

FIG. 5a represents the bottom end portion of a capsule for food or beverage preparation, before injection of fluid into the chamber 10. The embodiment of FIG. 5a corresponds to the embodiment of FIG. 2. The membrane 9 has a part surrounded by the adhesive seal band 11 of greater dimensions than the flat surface surrounded by said adhesive seal band (i.e. in the present case of greater dimensions than the opening at the bottom end of the chamber 10). The membrane 9 forms a dome over said opening.

Compared to the embodiment of FIG. 5a , in the embodiment of FIG. 5b the membrane is folded in the initial state (before preparation of the food or beverage product), so as to have an apparent flat shape over the opening at the bottom end of the chamber 10. The folds of the membrane can have a determined or erratic configuration. The apparent flat shape of the membrane 9 increases the space available for the ingredient inside the chamber 10.

In FIG. 5c , as in FIG. 4b , a fluid such as water and/or water vapour is introduced under pressure (i.e. above atmospheric pressure) into the chamber 10 formed within the capsule body 2. The pressure rises inside the chamber 10. The pressure is applied to the body walls 3 and to the membrane 10. The pressure difference between the interior of the capsule (chamber 10) and the exterior of the capsule, in particular under the membrane 9, generates a force distributed over the membrane surface which closes the opening surrounded by the rim 12. This force pushes the membrane 9 in a direction from inside to outside the chamber 10. The membrane 9 thus engages the opening means 15.

Thanks to the configuration of the membrane in a capsule according to the present invention, extra surface is provided for conformation of the membrane to the shape of the raised elements 17 of the opening means (or, generally speaking, for conformation of the membrane to the shape of the opening means). Compared to the membrane of a prior-art capsule, the membrane 9 of a capsule according to the invention can enter deeper into the spaces 18 between the pyramidal raised elements 16. It covers a greater percentage of the surface of the face of the opening means facing the membrane. For example, the membrane 9 can be dimensioned to obtain a coverage of more than 60%, and preferably more than 70% of this surface before said membrane opens.

With a capsule according to the present invention, the conformation of the membrane to the shape of the opening means is more regular over the whole surface of the membrane (or, more precisely, over the whole surface of the part of the membrane facing the opening means).

As shown in FIG. 5d , the pressure rises in the chamber 10 with introduction of fluid until it reaches the opening pressure. The membrane is pressed against the opening means by the force generated by the pressure difference between the pressure inside the chamber 10 and the atmospheric pressure outside said chamber 10. When the opening pressure is reached, the membrane opens (i.e. is pierced, cut, or torn) as shown in FIG. 5c thanks to the sharp design of raised elements 16 of the opening means 15. The food or beverage product obtained flows through the membrane 9 and the opening means 15, and is correctly filtered by these means to avoid too many particles of ingredient being present in the product delivered by the dispensing opening 8.

Thanks to the better conformation of the membrane to the shape of the opening means, a regular opening can be obtained over the whole surface of the membrane in contact with the opening means. In the represented example embodiment, the membrane after opening presents evenly distributed openings formed by the top of each pyramidal opening element. This also results in a constant and thus more predictable pressure inside the chamber 10 when a food or beverage is prepared from one capsule to another. An effective filter function is provided by the cooperation between the membrane and the opening means. Finally, a constant quality and taste of the product is provided.

It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be covered by the appended claims. 

1. Capsule for food or beverage preparation, the capsule comprising: a hollow body which is impermeable to liquids and to air and adapted to be punctured for fluid injection inside the capsule, a chamber formed inside the body and containing an ingredient for preparing food or beverage by dissolution into the fluid under pressure or extraction by the fluid under pressure, a membrane fastened to the body to retain pressure in the chamber, at least part of the membrane covering an opening formed in a bottom end of the chamber, the opening being surrounded by a rim to which an edge of the membrane is fastened by a fastening member which forms a seal between the body and the membrane, an opening member located outside the chamber in the vicinity of the membrane, the opening member being configured to open the membrane when the membrane is pressed against the opening member under an opening pressure, and the part of the membrane which is surrounded by the seal has a developed surface area comprised between 110% and 140% of the area of a flat surface surrounded by the seal.
 2. Capsule according to claim 1, wherein the opening formed in a bottom end of the chamber has an area of about 600 mm² while the part of the membrane which covers this opening has a developed surface area of more than 660 mm².
 3. Capsule according to claim 1, wherein the fastening member comprises an adhesive seal band.
 4. Capsule according to claim 1, wherein the membrane is formed from a flat sheet having a periphery of greater length than a periphery of the rim which surrounds the opening, the length of the periphery of the membrane in excess compared to the length of the periphery of the opening rim being evenly distributed along the periphery of the opening rim.
 5. Capsule according to claim 1, wherein the opening formed in the bottom end of the chamber is substantially circular, and the membrane forms a dome over the opening formed in the bottom end of the chamber when a pressure is established in the chamber greater than the pressure outside the chamber.
 6. Capsule according to claim 1, wherein the part of the membrane which covers the opening formed in the bottom end of the chamber comprises folds so as to be substantially flat when the pressures on each side of the membrane are balanced, and wherein the membrane can be at least in part unfolded under the effect of a pressure established in the chamber.
 7. Capsule according to claim 1, wherein the opening member comprises a plate having an upper surface facing the membrane, and wherein the upper surface forms or carries sharp raised elements.
 8. Capsule according to claim 7 wherein the raised elements are pyramids or truncated pyramids.
 9. Capsule according to claim 7, wherein the part of the membrane which covers the opening formed in the bottom end of the chamber has a surface area of more than 60% of the developed surface area of the plate.
 10. Capsule according to claim 1, wherein the membrane is made of aluminium, or of a laminate structure comprising an aluminium foil and a polymer layer.
 11. Capsule according to claim 1, wherein the membrane is made of plastics with a metallic covering.
 12. Capsule according to claim 1, wherein the membrane comprises pre-weakened spots.
 13. Capsule according to claim 1, wherein the material of which the chamber is formed is selected from the group consisting of aluminium, aluminium/plastics composite, aluminium/plastics/paper composite, and plastics in a single layer and in a multilayer form.
 14. Capsule according to claim 1, wherein the ingredient contained in the chamber comprises ground roasted coffee to be extracted into water vapour and/or hot liquid water or comprises a soluble ingredient or mix of soluble ingredients for preparation of a beverage. 